#!/usr/bin/env -S node --trace-warnings

/*
  micro http2 server with file monitoring and automatic app rebuild
  - can process concurrent http requests
  - monitors specified filed and folders for changes
  - triggers library and application rebuild
  - any build errors are immediately displayed and can be corrected without need for restart
  - passthrough data compression
*/

const fs = require('fs');
const zlib = require('zlib');
const path = require('path');
const http2 = require('http2');
const chokidar = require('chokidar');
const process = require('process');
const esbuild = require('esbuild');
const log = require('@vladmandic/pilogger');

// app configuration
// must provide your own server key and certificate, can be self-signed
// client app does not work without secure server since browsers enforce https for webcam access
const options = {
  key: fs.readFileSync('/home/vlado/dev/piproxy/cert/private.pem'),
  cert: fs.readFileSync('/home/vlado/dev/piproxy/cert/fullchain.pem'),
  root: '.',
  default: 'index.html',
  port: 8000,
  monitor: ['package.json', 'config.js', 'demo', 'src'],
};

// just some predefined mime types
const mime = {
  '.html': 'text/html',
  '.js': 'text/javascript',
  '.css': 'text/css',
  '.json': 'application/json',
  '.png': 'image/png',
  '.jpg': 'image/jpg',
  '.gif': 'image/gif',
  '.ico': 'image/x-icon',
  '.svg': 'image/svg+xml',
  '.wav': 'audio/wav',
  '.mp4': 'video/mp4',
  '.woff': 'application/font-woff',
  '.ttf': 'application/font-ttf',
  '.wasm': 'application/wasm',
};

// keeps esbuild service instance cached
let es;

// rebuild on file change
async function build(f, msg) {
  log.info('Monitor: file', msg, f);
  if (!es) es = await esbuild.startService();
  // common build options
  const cfg = {
    minify: false,
    bundle: true,
    sourcemap: true,
    logLevel: 'error',
    platform: 'browser',
    target: 'es2018',
    format: 'esm',
    external: ['fs'],
  };
  // only rebuilding esm module and demo application
  // for full production build use "npm run build"
  try {
    // rebuild library fist
    cfg.entryPoints = ['src/human.js'];
    cfg.outfile = 'dist/human.esm.js';
    cfg.metafile = 'dist/human.esm.json';
    await es.build(cfg);
    // then rebuild client app so it can use freshly rebuild library
    cfg.entryPoints = ['demo/browser.js'];
    cfg.outfile = 'dist/demo-browser-index.js';
    cfg.metafile = 'dist/demo-browser-index.json';
    await es.build(cfg);
    log.state('Build complete');
  } catch (err) {
    log.error('Build error', JSON.stringify(err.errors || err, null, 2));
  }
}

// watch filesystem for any changes and notify build when needed
async function watch() {
  const watcher = chokidar.watch(options.monitor, {
    persistent: true,
    ignorePermissionErrors: false,
    alwaysStat: false,
    ignoreInitial: true,
    followSymlinks: true,
    usePolling: false,
    useFsEvents: false,
    atomic: true,
  });
  watcher
    .on('add', (evt) => build(evt, 'add'))
    .on('change', (evt) => build(evt, 'modify'))
    .on('unlink', (evt) => build(evt, 'remove'))
    .on('error', (err) => log.error(`Client watcher error: ${err}`))
    .on('ready', () => log.state('Monitoring:', options.monitor));
}

// get file content for a valid url request
function content(url) {
  return new Promise((resolve) => {
    let obj = { ok: false };
    obj.file = url;
    if (!fs.existsSync(obj.file)) resolve(null);
    obj.stat = fs.statSync(obj.file);
    // should really use streams here instead of reading entire content in-memory, but this is micro-http2 not intended to serve huge files
    if (obj.stat.isFile()) obj.ok = true;
    if (obj.stat.isDirectory()) {
      obj.file = path.join(obj.file, options.default);
      obj = content(obj.file);
    }
    resolve(obj);
  });
}

// process http requests
async function httpRequest(req, res) {
  content(path.join(__dirname, options.root, req.url)).then((result) => {
    const forwarded = (req.headers['forwarded'] || '').match(/for="\[(.*)\]:/);
    const ip = (Array.isArray(forwarded) ? forwarded[1] : null) || req.headers['x-forwarded-for'] || req.ip || req.socket.remoteAddress;
    if (!result || !result.ok) {
      res.writeHead(404, { 'Content-Type': 'text/html' });
      res.end('Error 404: Not Found\n', 'utf-8');
      log.warn(`${req.method}/${req.httpVersion}`, res.statusCode, req.url, ip);
    } else {
      const ext = String(path.extname(result.file)).toLowerCase();
      const contentType = mime[ext] || 'application/octet-stream';
      const accept = req.headers['accept-encoding'] ? req.headers['accept-encoding'].includes('br') : false; // does target accept brotli compressed data
      res.writeHead(200, {
        'Content-Language': 'en', 'Content-Type': contentType, 'Content-Encoding': accept ? 'br' : '', 'Last-Modified': result.stat.mtime, 'Cache-Control': 'no-cache', 'X-Powered-By': `NodeJS/${process.version}`, // 'Content-Length': result.stat.size,
      });
      const compress = zlib.createBrotliCompress({ params: { [zlib.constants.BROTLI_PARAM_QUALITY]: 5 } }); // instance of brotli compression with level 5
      const stream = fs.createReadStream(result.file);
      if (!accept) stream.pipe(res); // don't compress data
      else stream.pipe(compress).pipe(res); // compress data

      // alternative methods of sending data
      /// 2. read stream and send by chunk
      // const stream = fs.createReadStream(result.file);
      // stream.on('data', (chunk) => res.write(chunk));
      // stream.on('end', () => res.end());

      // 3. read entire file and send it as blob
      // const data = fs.readFileSync(result.file);
      // res.write(data);
      log.data(`${req.method}/${req.httpVersion}`, res.statusCode, contentType, result.stat.size, req.url, ip);
    }
  });
}

// app main entry point
async function main() {
  log.header();
  await watch();
  const server = http2.createSecureServer(options, httpRequest);
  server.on('listening', () => log.state('HTTP2 server listening:', options.port));
  server.listen(options.port);
}

main();